Heat oven to 375 degrees F.,Brown meat with peppers and onions in large skillet on medium-high heat.,Stir in chili powder; cook 1 min.,Add salsa and corn; mix well.,Simmer 5 min.,Spread 2 cups meat sauce onto bottom of 13x9-inch baking dish; top with layers of 2 tortillas, 1 cup meat sauce, sour cream and 1/2 cup cheese.,Cover with 2 tortillas, 2 cups meat sauce and 1/2 cup cheese; top with remaining tortillas and meat sauce.,Cover.,Bake 30 min.,or until casserole is heated through.,______,or until melted.